I never founded a group myself. But maybe can give a few pointers. First make sure you actually want to do that. Going to other groups as guest is free and easy, and you can check out if the structure of the Organization is something you like. Then you need a few like-minded people. There is a minimum number for new groups. Keep in mind that it is a training group for speaking in general. One does not practice to convince in a specific topic, but the speaking itself - which would classify it as a dark art, and maybe not even be what you look for. For the actual founding the easiest way is to contact another local group and ask for assistance. There is some paperwork, and then holding the regular meetings. Having a few experienced members is a really good way to get a new group going.